This invention relates to imageable compositions and to methods of utilizing said compositions. More particularly, it relates to imageable compositions capable of forming color when exposed to electromagnetic radiation in one wavelength range and capable of being stabilized against color formation when exposed to electromagnetic radiation in a different wavelength range.
The use of radiation sensitive compositions to form colored images has previously been suggested (e.g., see U.S. Pat. Nos. 3,390,994; 3,390,996 and 3,658,543). The compositions disclosed in these patents comprise a leuco form of dye, a photooxidant, and a combination of oxidizable and reducable components (the combination often referred to as redox couples). The oxidizable components of these compositions participate in color formation when the composition is exposed to radiation in one wavelength range while the reducable components participate in preventing color formation when the composition is exposed to radiation in another wavelength range. Frequently the wavelength ranges overlap so that care must be taken in selecting the oxidizable and reducable components to insure they each are sensitive to different activating radiations. Additionally, special filters must often be employed during each step in order to prevent premature activation of the other step.
U.S. Pat. No. 3,615,454 discloses another type of radiation sensitive composition. This composition comprises a leuco form of a dye, a photooxidant and a radiation-sensitive ethylenically-unsaturated polymerizable component. These compositions preferably employ an oxygen barrier that is transparent to the radiations used during the stabilization step.
The present invention provides novel compositions that do not require special selection of oxidizable and reducable components, or the use of special filters during color formation. Moreover the compositions of the present invention do not employ oxygen barriers.
Compositions of the present invention have a variety of uses. For example they are especially useful whenever substantially permanent images or color proofs are required such as in pattern making, printing, photography, etc. Additionally they may be used to provide positive or negative images merely by changing the order of exposure to the activating irradiations through one stencil thereby eliminating the need for preparing both positive and negative stencils.